1. Field of the Invention
The present invention is directed to porous groyne-like structures and method for their use in reclaiming beaches, shoreline areas and other land masses which are subject to erosion by natural forces and, more specifically, to permanent and semi-permanent groyne structures which may be left in place when deployed or selectively vertically raised during use. In some embodiments the groynes may be systematically raised as reclamation progresses from the buildup of silt, sand, shells, dirt, twigs and branches, grasses and other materials.
2. Description of Related Art
Beach and other shoreline erosion, especially in coastal areas, is a major concern to property owners who have residences or establishments which are situated in close proximity to the shoreline. Not only is there a tremendous personal and economic loss caused by damage to, or loss of, real estate, housing and commercial buildings by shoreline or beach erosion, but there is also recreational loss of waterfront property which adversely affects the general public.
To deter coastal erosion in many areas, large seawalls are constructed to prevent high tides from reaching land and property. Such structures are costly and are only practical when population densities make it economically reasonable to construct them. Further, such structures have an adverse effect on the natural appearance of the shoreline and, in many areas, cannot be practically constructed.
Other methods of shoreline reclamation include creating jetties or artificial barriers or reefs which extend from the shoreline. These structures are permanent installations and are generally utilized to prevent sand along coastal areas from washing out to sea by wave action. Like seawalls, however, such structures are costly to construct and maintain and, in some areas, are not appropriate for use due to the shoreline configuration, prevailing currents or tidal activity and the like. Also, such structures create a safety hazard in areas where recreational activity is anticipated
A further method for reclaiming shoreline areas and preventing erosion is the placement of off-shore, underwater barriers. Often, large porous structures are placed along a sea floor or riverbed at some distance from the existing shoreline. The structures are provided to break wave, current or tidal action thereby creating a zone of low velocity water flow adjacent a beach or riverbank so that sand, silt and other particulate material will settle out of the water before being conveyed by fluid currents out from the shoreline. Again, such outer barriers are only appropriately used in some locations and are not appropriate for use in many locations and may be objectionable for use in some areas due to the adverse affect on aquatic life.
Other methods which are widely used to reclaim shorelines or beaches are dredging and sand importation. When major dunes along a shoreline are damaged or washed away during heavy storms, it is often necessary to import new dirt and sand to re-establish the dunes to provide a natural barrier to tidal activity. Dredgers are commonly utilized to pump sand from a sea floor or riverbed to build up natural barriers. Such methods of shoreline reclamation, however, are temporary measures, at best, and do not provide a long-term solution to shoreline erosion. Further, such restoration methods are extremely costly and are not practical in many locations.
In view of the foregoing, there is a need to provide a method and apparatus for economically reclaiming damaged shorelines, and other land mass beach areas which can be practically used without an adverse effect to either land or water environments. In U.S. Pat. Nos. 1,969,123 and 4,710,056, methods and structures for beach restoration are disclosed which utilize netting for purposes of trapping sand, shells and other particulate matter carried by wave action. Nets are extended outwardly from the shoreline and are left in place until a buildup of sand and other particulate matter is established after which the nets, which may be buried several feet or more in the newly collected material, are withdrawn by winches or other means. The removal of the netting material can adversely affect the restored shoreline by creating trenches or furrows which form natural channels in which water flows away from the shoreline thereby conveying particulate matter back to a body of water.
In prior U.S. Pat. Nos. 5,720,573 and 5,944,443, screen or netting structures for groynes are disclosed wherein the screens are periodically raised as material is deposited during reclamation so as to reduce interference with newly deposited materials. During use, flexible materials such as screening and netting are effective for material build-up, however, under some deployment conditions such as during violent storms and sea surges, such groyne structures can be significantly damaged. Damage to screening or netting mandates added cost for required repair and replacement in order to maintain an effective groyne system.
Also, many groyne systems, such as described in the aforementioned patents, are specifically designed to be removably deployed. In some areas, such as along coastal or other shorelines it may be more beneficial to deploy or erect groyne systems which are designed to be semi-permanent or permanent. Such groyne systems must be constructed to with stand the forces encountered including wind, wave and tidal action over extended periods of time.
The present invention is directed to a method and apparatus for reclaiming shoreline, beach and offshore areas which includes the installation of semi-permanent or permanent groyne structures defined having a plurality of posts or stanchions which are embedded in a sea floor, or in other areas, so as to be in spaced relationship with respect to one another, such as extending from a shoreline to an off shore area and between which are mounted one or more porous screens. The stanchions may be generally aligned in spaced relationship with one another or may be staggered in offset relationship. In some preferred embodiments, the stanchions may be placed in sets which include at least two end stanchions to which the screens are secured. As used herein, the term shoreline refers to both land and off shore bottom areas including beaches and banks situated along lakes, rivers, inlets, bays, seas, oceans and the like, it being the express purpose of the invention to build-up solid material deposits both on and off shore.
The screens of the present invention are formed in the preferred embodiments of a molded, laminated or extruded open plastic mesh or open grid material. A preferred material is Tensar Geo-grid(copyright) which is an integrally formed grid structure manufactured of stress resistant high density polyethylene or polypropylene or other polymers, co-polymers or polymer mixtures or laminates thereof and sold by Earth Technologies, Inc. of Atlanta, Ga. Such grids can be formed to provide uniaxial properties or biaxial properties with the mesh openings between cross-members of the grids varying in size depending upon anticipated use.
The screens are mounted on stanchions or poles which are embedded into the sea floor or into other soil preferably by clamping or otherwise securing end edges of separate screens to sleeves which are slidably disposed about the spaced stanchions. In this manner, when the screens are originally installed, the lower edges thereof rest on and become temporarily embedded in deposited material forming a new land mass. The screens can be left in place when deployed or they may be elevated with respect to newly deposited material such that the lower edges rest on or remain slightly embedded in the newly deposited material. Means for elevating each screen may include hoists, cranes and the like which are positioned adjacent the groyne structures. The hoist may be selectively secured to either the sleeves or to the screen material in order to provide a lifting force so as to slide the supporting sleeves vertically upwardly relative to the spaced stanchions.
To further facilitate the manner in which the screens of the present invention may be elevated, in preferred embodiments, each screen is secured at its ends to stanchions on the sleeves not supporting other screens, however, in some embodiments the stanchions or sleeves may support adjacent screens in end-to-end relationship. In some embodiments, when separate pairs of end stanchions are used to support separate screens in generally end-to-end relationship, adjacent stanchions of the pairs may be connected to one another such as by clamps, rings or other connections such that the forces directed against one of the joined stanchions are distributed to, and resisted by, the other stanchions.
As a further improvement, in some embodiments, each screen may be subdivided into separate vertical sections each of which may be secured to a plurality of separate sleeves movably mounted on end supporting stanchions. In this manner, as the screen sections are raised, the uppermost sections can be removed from the groyne structure as is necessary.
Whether or not a single vertical screen or a plurality of vertical screens are used between spaced stanchions, in preferred embodiments the mesh openings of the screens should be smaller adjacent the lower portion of the groyne structures, although in some embodiments the mesh opening may be uniformed throughout the groyne structures. Further, the mesh openings may be of varied configuration and may be elongated and non-rectangular, rectangular, square or other configuration and be within the teachings of the present invention. The size of the mesh openings, may vary. The openings may be created by forming the mesh openings at varied dimensions during manufacture or may be constructively formed by overlapping separate screen grids so as to define openings of different sizes. This can be accomplished by placing two screen grids in face-to-face relationship with respect to one another such that their openings are not aligned and securing such face-to-face screens to sleeves slidably mounted on common end stanchions.
As a variation of the preferred embodiment, the screen grids may be formed so as to permit a weaving of either the sleeves or the stanchions between vertically spaced openings in each screen. In this manner, a screen may be directly secured without mechanical fasteners to a stanchion or to a sleeve slidably mounted on a stanchion. This may be preferred where a screen has a significant horizontal length so as to allow an intermediate portion of the screen to be secured in a relatively inexpensive manner to an intermediate stanchion.
As opposed to directly mounting the screens to the sleeves or stanchions of the invention, various fasteners may be utilized to secure portions of the screens directly to the sleeves or stanchions. Such fasteners may be clamps constructed of plastics or metal. Further, the sleeves may be cylindrical sleeves or may be molded sleeves having flanges which may be secured to the ends of the screens. In some embodiments, the sleeves may be formed as split sleeves having outwardly extending flanges between which an end portion of a screen may be secured, such as by of the use of bolts or other fasteners, fusing, welding or other means.
Utilizing the methodology of the present invention, a plurality of spaced groyne structures are positioned so as to extend in spaced relationship with respect to one another such as outwardly from a shoreline. The orientation between the groyne structures and the angular relationship with respect to other areas or land masses, such as a shoreline, will be dictated by the specifics of a given area including winds, currents, tidal activity and the like. Once the screens have been secured to the stanchions, the screens may be left in place as semi-permanent or permanent structures or they may be elevated periodically as deposits are formed so as not to become too deeply embedded in the newly deposited material and thus not disturb the newly deposited material.
It is the primary object of the invention to provide a method and apparatus for economically reclaiming land including along shorelines and off shore areas of oceans, gulfs, inlets, bays, rivers, lakes as well as other areas where currents, tidal and/or wind activity is experienced and wherein the structures exhibit permanent or semi-permanent characteristics being sufficiently strong and rigid to withstand stresses imparted thereto by strong storm surges and heavy tidal activity.
It is a further object of the invention to provide groyne structures and a method for installing such structures wherein the structures may be temporarily installed and removed after land has been reclaimed without disturbing the natural contour of the reclaimed land.
It is also an object of the invention to provide groyne structures to reclaim land which are environmentally compatible and which will not deteriorate by exposure to normal environmental conditions including ultra-violet light or sea water.